I guess it depends on what you mean by staggering. If you mean different size wheels and tires between the front and back, that is bad. However if you are only referring to width, that is possible but also has its challenges.
For the xDrive to operate correctly the outside tire diameter has to be identical so that the transfer case can distribute power correctly. If all 4 wheels are 20"s and you run 9" width in front and 10" width in back, that is fine if you match the aspect ratio of the tires to achieve exact diameters. That is not always the case so you have to get the technical data on the tires to be sure. The other challenge is long term wear. With 4 matching tires, they can be rotated to maintain even wear. With staggered tires the fronts and rear cannot be switched. The primary drive wheel (rear) will wear faster so it is essential to monitor tire diameter over time to not destroy the transfer case. Here is a video on staggering on an xDrive. It can be done as long as you check all the boxes.
Lowering also requires attention to detail. The front axles have extra drive shaft components that take up room and have to maintain a certain alignment and camber with the control arms. That is the primary reason xDrive cars ride a little higher than non-xDrive. I've read a bunch of articles that say 1/2" lower is good to go. 1" or greater and the front drive wears prematurely.
xDrive is a really advanced design but it does have its limitations when it comes to mods.